1. Field of the Invention
The present invention relates to laser systems for medical treatments and in particular, for laser surgical procedures. More particularly, it relates to optical fiber systems and methods used for surgical treatment of various medical conditions, including benign prostatic hyperplasia (BPH).
2. Invention Disclosure Statement
Numerous medical applications (e.g. endoluminar treatment of varicose veins, laser treatment of BPH or of hemorrhoids) require the treatment of a target tissue area that is not directly in front of the fiber but located sideways. As many of those therapies have to be performed intra-corporal in an environment providing only reduced space, the direct positioning and pointing of the fiber tip of a so-called bare fiber is not applicable.
Fiber optical probes with tailored emission characteristics (e.g. side firing fibers) are feasible for those treatment procedures and turned out to be advantageous. Many attempts to use reflection effect to direct light laterally have been proposed.
Among the earliest, Abe et al teaches in U.S. Pat. No. 4,740,047 a side fiber constructed such that a transparent tubular member is coupled to the forward end portion of a fiber through two coating layers, and an anti-reflection coating layer is formed on a laser beam exiting surface of the transparent tubular member. The clad-core dimensions of examples were about 1.5 to 1. Also, U.S. Pat. No. 5,292,320 by Brown et al discloses an optical fiber, having a core and a cladding wherein the cladding has a refractive index smaller than the core, having an input end suitably configured to connect to an appropriate radiation source and having a distal end in the proximity of which two or more grooves are penetrating into the core. The grooves have at least partial reflector capability so as to deflect radiation thereto radially in one or more predetermined patterns. In one embodiment this invention has a fused proximal end of cover tube over distal end cladding of the fiber to create an air gap over structured distal tip. Another example of recent prior art in side fibers can be appreciated in U.S. Pat. No. 5,509,917 by Cecchetti et al. A side fiber is presented wherein laser beam in the optical fiber is totally reflected down toward the side of the fiber using an obliquely cut tip due to the refractive index differences between the fiber core and that of the air gap formed in the cap, and with the cap in the path of radiation transmission can be fused to the clad fiber at the distal end to reduce/eliminate Fresnel loss as the side firing fiber transmits the laser energy. Another example is found in U.S. Patent Application No. 2007/0106286 by Harschack et al. which propose a side fire optical fiber tip for high power applications. A predetermined length of an output tip on the distal end of the optical fiber is formed with an optical fiber core and cladding layer of preselected thickness wherein the cladding to core diameter ratio is 1.2. Over optical fiber output end, a silica capillary tube is fused to the exposed cladding. These types of fiber probes direct the optical radiation into the desired direction as they take advantage of the effect of total reflection at a boundary layer with a feasible refractive index step, i.e. where the refractive index on the other side of said boundary layer is significantly lower than inside the glass optical fiber. Mostly, the fiber tip is encapsulated in a sealed cap together with a small volume of air. The enclosed air provides the necessary refractive index step which allows for the redirection of the optical radiation guided by the glass optical fiber. Furthermore, the end cap protects the structured fiber end tip from environmental influences and thus e.g. prevents it from mechanical damage and protects the patient from injuries.
Hanley et al in US Application Publication 2009/0287198 A1, presents an apparatus that includes a distal of an optical fiber core having a multilayer dielectric coating, disposed on an angled surface at the core distal end to produce internal reflection of laser energy at the angled surface, the coating and angled surface collectively configured to redirect laser energy in a lateral direction. Brekke et. al, in U.S. Pat. No. 7,463,801 proposes a side fiber having both a core and a cladding surrounding the core. The optical fiber terminates at a distal tip having a surface inclined relative to the axis of the fiber. A tubular member surrounds the optical fiber at its distal end. The distal end of the optical fiber has a portion opposing the tubular member for being united to the tubular member. The distal portion is joined to the tubular member by an intermediate material selected to have an index of refraction matching that of the core and the tubular member. U.S. Pat. No. 5,366,456 by Rink et. al discloses a device with a firing tip which has an insert with a highly polished mirrored surface lying at a specific angle with respect to the longitudinal axis of the optical fiber. Thus, impinging laser radiation is reflected to the side and delivered at a right angle to the fiber.
As can be appreciated, once again, these are complex configurations that try to achieve appropriate refraction index difference combinations between different materials to reflect radiation in the desired direction. The end cap is glued and/or fused to the glass optical fiber. Thus, the distal endings of those fiber probes are often bulky and difficult to produce. Furthermore, the bonding of end cap and glass optical fiber might suffer from a reduced damage threshold, especially in those cases where fiber and cap are glued and the treatment requires high optical energy. Additionally many of these inventions require a relatively large probe diameter. Many minimal invasive treatment procedures require the delivery of the glass optical fiber through an endoscope. Therefore, the maximum outer diameter of a medical probe is limited by the inner diameter of the endoscope's channel. Typically, this inner diameter is of the order of 2 mm.
There is thus, a need to provide such instruments and methods as further described by the present invention.